A set of temperature sensitive mutants of polivirus Type 1 has been isolated by hydroxylamine mutagenesis and replica plating on HeLa cells at 33 degrees C (permissive) and 39 degrees C (restrictive). One of these mutants, tsB9, has been shown to be defective in an early step in RNA synthesis required for production of mature 35S viral RNA. This set of mutants will be characterized biochemically with emphasis on viral RNA species produced, viral RNA polymerase activity and processing of viral proteins and assembly of viral particles. In another set of experiments, recombinant DNA clones containing sequences representing all or part of the poliovirus Type 1 genome will be used to probe conserved regions among various enterovirus genomes, employing R-loop techniques. In addition, the interaction of viral and host proteins with viral RNA or recombinant DNA representing portions of the viral genome will be investigated. These proteins, isolated as nucleoprotein complexes, will be examined for binding to specific regions of the viral genome. These data will be used to test the hypothesis that certain genome sequences, important for regulation during viral gene expression, are highly conserved among various enteroviruses.